Controlling heat flow, airflow, moisture flow and solar radiation will control the interactions between the physical elements of the building, its occupants and the environment.

Of these four, airflow merits major consideration mainly because of its influence on heat and moisture flow.

Airflow carries moisture that impacts on the materials’ long-term performance and durability. Airflow also affects a building’s behaviour in a fire, indoor air quality and thermal energy use. One of the key strategies in the control of airflow is the use of air barriers.

Air barriers are systems of materials designed and constructed to control airflow between a conditioned space and an unconditioned space. The air barrier system is the primary air enclosure boundary that separates indoor air and outdoor air. Air barrier systems also typically define the location of the pressure boundary of the building enclosure.

Do buildings in a hot climate need an air barrier?

If buildings lacks a good air barrier, lots of cool indoor air can escape through cracks in your walls and ceiling. That departing cool air is replaced by hot outdoor air that sneaks in cracks, forcing air cooling systems  to work overtime. If summers are humid, these air leaks carry a double penalty.

Spray foam to make houses as airtight as possible

Many builders have achieved very low levels of air leakage without any spray foam at all. Moreover, many homes that have been insulated with spray foam still have high levels of air leakage.

The reason is simple: most walls and ceilings don’t leak in the middle of the wall or ceiling. They leak at edges, penetrations, and transitions. So even when a wall is insulated with spray foam, you still need to worry about the details.

The lowest levels of air leakage are achieved by builders who have studied airtight construction techniques, who think through potential air leakage paths during each phase of construction, who are conscientious and methodical, and who have already built a few homes that have been pressure tested.

Attention to detail usually matters more than high-tech tools or equipment.

The Blower Door Test.

Tracking down air leaks can be tricky, especially for builders or homeowners who are unfamiliar with the devious paths that air can take. For example, builders are often surprised to learn that significant air leakage paths can occur through interior partitions located far from exterior walls.

The best way to test the integrity of a home’s air barrier is to perform a blower-door test.

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